1. Field of the Invention
The present invention generally relates to a photo signal processing apparatus and, more particularly, to a photo signal processing apparatus utilizing a charge accumulation type light receiving unit such as, for example, a charge coupled device (CCD), including a plurality of photosensor elements for receiving light, which is operable to perform data processing based on data fed from the light receiving unit.
2. Description of the Prior Art
This type of photo signal processing apparatus is disclosed, for example, in the Japanese Laid-open Patent Publication No. 60-125817. According to this publication, when accumulation completes in the light receiving unit of charge accumulation type, the next succeeding accumulating operation is performed. However, a data processing means for carrying out data processing in response to data from the light receiving unit does not accept any data from the light receiving unit during the data processing.
In such case, even if the accumulation of the light receiving unit completes during the data processing of a previous accumulation because a target object is of high brightness, the data resulting from the completion of the accumulation will not be inputted in overlapping relationship with the data processing of the previous accumulation data occurring parallel to this accumulation. It is only where the accumulation of the light receiving unit requires a relatively long time because of the low brightness of the target object, that the charge accumulation for the next data processing can be carried out during the data processing of the previous accumulation so that the time required to complete a single focus detecting operation can be rendered to be smaller than the sum of the charge accumulating time of the light receiving unit and the data processing time.
However, according to the prior art data processing apparatus of the type described hereinabove, as shown in FIG. 14 of the accompanying drawings, in the event that the charge accumulation 3 and 6 of the light receiving unit takes place parallel to a final stage of the data processing 1 and 2, but occurs shortly before the termination of the data processing 1 and 2, a signal associated with the charge accumulation 3 and 6 cannot be utilized because the data processing 1 and 2 has not yet been terminated. Therefore the next succeeding data processing 2 and 3 can only be initiated in response to a signal associated with the subsequent charge accumulation 4 and 7.
Because of the above, it often happens that the signal data processing cycle tdc is equal to or substantially equal to the sum of the time ti required for the charge accumulation of the light receiving unit and the time Td required for the data processing, and, therefore, the data processing speed at the time the data processing is repeatedly carried out tends to be lower than possible.